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Biomedical subjects

J L Davis

Publications and source records attributed to J L Davis.

At least 19 recordsLinked to original sources
PubMed1992

Causes of reduced visual acuity on long-term follow-up after cataract extraction in patients with uveitis and juvenile rheumatoid arthritis.

We reviewed the long-term follow-up on a consecutive series of 16 eyes from ten patients with juvenile rheumatoid arthritis-associated cataracts that were removed by using pars plana lensectomy and vitrectomy. All patients had prominent cataracts, chronic uveitis, posterior synechiae, and vitreitis preoperatively, and had at least 12 months of follow-up postoperatively. The median length of follow-up was 51 months (range, 12 months to ten years). In the early postoperative period, a visual acuity of 20/70 or better was obtained in 13 of 16 eyes (81%). With longer follow-up, the final visual acuity was 20/70 or better in only nine of 16 eyes (56%). The primary categories of delayed visual loss in these cases were glaucoma and macular disease (chronic cystoid macular edema, macular hole, hypotony maculopathy, and recurrent macular pucker). Despite these limitations in maintaining good visual acuity, a pars plana lensectomy and vitrectomy approach is effective for cataracts in these patients with uveitis.

Adolescent↗
PubMed1992

Immunocytochemical staining of vitreous cells. Indications, techniques, and results.

Diagnostic vitrectomy is often performed because of suspected infection or malignancy. Giemsa, Gram, and Papanicolaou stains are used routinely to identify the components in the vitreous. Immunocytochemical staining of cellular components of vitreous specimens has the potential to significantly increase the amount of useful information that can be gained from histopathologic study. Vitreous specimens from 14 patients undergoing diagnostic or therapeutic vitrectomy for infection, suspected primary intraocular lymphoma, or uveitis were examined by immunocytochemical staining using monoclonal antibodies specific for leukocyte subclass antigens and immunoglobulin. The three classes of disorders showed characteristic patterns of staining, which were useful in confirming microbiologic and clinical diagnoses. Infections showed more pronounced neutrophils and macrophages, primary intraocular lymphomas demonstrated light chain restriction of the malignant B lymphocytes, and uveitis was characterized by the predominance of T lymphocytes. The routine use of immunocytochemical staining is recommended to characterize cellular infiltrates and increase the diagnostic yield from vitrectomy specimens.

Antibodies, Monoclonal↗
PubMed1992

Management of retinal detachment associated with CMV retinitis in AIDS patients.

In patients with AIDS, the most important ocular opportunistic infection, CMV retinitis, can now be treated effectively with virostatic agents. Associated retinal detachment is encountered frequently, and its management has become increasingly significant to quality of life as improvements in medical care have helped to preserve vision and extend life expectancy. Although retinal detachment in these eyes is typically rhegmatogenous, the pathophysiology is distinctive due to the association with CMV retinitis which, even in remission, is characterised by atrophic changes at all levels of affected retina and alterations of the vitreous. Despite initially successful surgical reattachment, multiple, small, often posterior holes may develop because of progressive CMV infection. For these reasons, vitrectomy and silicone oil injection with scleral buckling may currently provide the best overall means of maintaining retinal reattachment and restoring visual function. Nevertheless, management must be individualised in each case, with the realisation that progressive visual loss frequently ensues from retinitis progression.

AIDS-Related Opportunistic Infections↗
PubMed1992

A presumptive helicase (MOT1 gene product) affects gene expression and is required for viability in the yeast Saccharomyces cerevisiae.

Exposure of a haploid yeast cell to mating pheromone induces transcription of a set of genes. Induction is mediated through a cis-acting DNA sequence found upstream of all pheromone-responsive genes. Although the STE12 gene product binds specifically to this sequence element and is required for maximum levels of both basal and induced transcription, not all pheromone-responsive genes are regulated in an identical manner. To investigate whether additional factors may play a role in transcription of these genes, a genetic screen was used to identify mutants able to express pheromone-responsive genes constitutively in the absence of Ste12. In this way, we identified a recessive, single gene mutation (mot1, for modifier of transcription) which increases the basal level of expression of several, but not all, pheromone-responsive genes. The mot1-1 allele also relaxes the requirement for at least one other class of upstream activating sequence and enhances the expression of another gene not previously thought to be involved in the mating pathway. Cells carrying mot1-1 grow slowly at 30 degrees C and are inviable at 38 degrees C. The MOT1 gene was cloned by complementation of this temperature-sensitive lethality. Construction of a null allele confirmed that MOT1 is an essential gene. MOT1 residues on chromosome XVI and encodes a large protein of 1,867 amino acids which contains all seven of the conserved domains found in known and putative helicases. The product of MOT1 is strikingly homologous to the Saccharomyces cerevisiae SNF2/SW12 and RAD54 gene products over the entire helicase region.

Adenosine Triphosphatases↗
PubMed1992

Complications of smooth pin fixation of fractures and dislocations in the hand and wrist.

A retrospective review of patients treated with internal fixation of fractures or dislocations of the hand or wrist over a four-year period was undertaken to determine the complication rates of pin fixation for stabilization of these injuries. One hundred thirty-seven patients who received 422 pins were studied. All pins were unthreaded, measured 0.035-0.069 inches (0.9-1.8 mm) in diameter, were placed with a power drill, and were left protruding through the skin. The mean time that pins were left in place was 6.5 weeks, (range, two days to 24 weeks). Minimum follow-up time was 43 days after pin removal. Thirty-four complications occurred in 24 patients, and the overall complication rate was 18%. Forty-five of the 422 pins were involved (11%). Complications included infections in ten patients (7%), pin loosening without infection in six (4%), loss of reduction in six (4%), symptomatic nonunion in six (4%), impaled flexor tendon in two (2%), asymptomatic pseudarthrosis in one (1%), pin migration in one (1%), median nerve injury in one (1%), and radial artery injury in one (1%). Osteomyelitis developed in two of the patients with infections. Pin tract infection occurred at a mean time of ten weeks and aseptic loosening at a mean time of eight weeks. The frequent complication rates emphasize the need for meticulous pin placement, adequate intraoperative evaluation of pin position, and satisfactory patient compliance. Despite the frequency of these complications, serious permanent sequelae did not occur in most patients.

Bone Nails↗
PubMed1991

Role of chorioretinal biopsy in inflammatory eye disease.

Two patients who had similar clinical presentations of bilateral multiple chorioretinal lesions and needed a correct diagnosis underwent chorioretinal biopsy. The biopsy from one patient demonstrated mainly a B cell infiltrate in choroidal and subretinal nodules, while the biopsy from the second patient showed mainly macrophages in the retina. These findings directed the therapeutic approach taken in each patient. Although chorioretinal biopsy is an invasive procedure with the potential for serious complications, the resultant finding may aid in the diagnosis and guide the subsequent management of certain patients presenting with serious ocular findings of undefined etiology.

Biopsy↗
PubMed1979

Studies of the electron-nuclear coupling between Fe(III) and 14N in cytochrome P-450 and in a series of low spin heme compounds.

We have observed the nuclear modulation pattern in the envelope of electron spin echoes for various low spin paramagnetic heme proteins including cytochrome c, myoglobin hydroxide, myoglobin mercaptoethanol, and cytochrome P-450, using the three-pulse-stimulated echo method. We have also carried out similar experiments with model compounds containing either [14N]- or [15N]imidazole. In many of the compounds studied, we have been able to identify the nuclear modulation effects arising from 14N of the porphyrin ring and have been able to characterize and interpret the modulation effects due to 14N of various nitrogenous axial ligands. We have found that the heme of low spin ferric cytochrome P-450 is coordinated to a nitrogenous ligand, probably imidazole. We have also demonstrated that the remote 14N of the imidazole ligand in a [14N]imidazole-heme-NO-model compound is coupled differently than in myoglobin nitroxide, demonstrating the direct effect of the protein of metal ligand bonding.

Binding Sites↗
PubMed1979

Interaction of bovine platelets with bovine glomerular basement membrane.

The interaction of bovine platelets with bovine glomerular basement membrane has been studied by aggregometry, transmission and scanning electron microscopy and measurement of [3H] serotonin release. In the absence of added calcium platelets adhere to basement membrane but fail to undergo the release reaction or aggregation. In the presence of 0.2-0.5 mM calcium release of serotonin and complete aggregation of the platelets are observed when sufficient basement membrane is present. Platelets were strongly adhered to the basement membrane surface, the platelet surface in the aggregates closely following the surface of the basement membrane. Platelet morphology in aggregates with basement membrane closely resembled that of platelets from collagen-induced aggregates. Basement membrane differed from collagen in its requirement for calcium for the aggregation and release reactions. In addition purified basement membrane was 1.5-3 fold less active on a weight basis than bovine tendon collagen in promoting aggregation.

Animals↗
PubMed1979

Memory enhancement induced in chicks by anesthetic doses of chlorpromazine.

Three experiments describe retroactive memory enhancement in chicks by chlorpromazine (CPZ), a potent membrane stabilizer at anesthetic doses. First, chicks trained on a one-trial peck suppression task under moderate aversant conditions and given 60--144 mg CPZ/kg, intraperitoneally, displayed increased memory retention 24 h later when compared with chicks given saline or 15--36 mg CPZ/kg. The second experiment confirmed the memory enhancement using a different moderate aversant on a different peck target and extended the effect to 48 h. The third experiment demonstrated the CPZ effect to be retrograde because the enhancement observed when CPZ was injected 1 min or 3 min after training did not occur when injection was delayed 4 h. One speculative interpretation of retrograde enhancement with CPZ includes the stabilization of swollen dendritic spines, which may facilitate neuronal pathways.

Anesthesia↗